The present invention relates generally to valves having an integral tap for piercing an otherwise sealed pipeline and, more particularly, to a unitized fixture having a piercing needle valve screw fitted within a single seal and secured within the fixture housing so as to prevent the complete removal of the valve screw.
In the service of various closed loop, pressurized gas systems, including refrigerant type systems in particular, there is often a need to access the system to recharge or discharge the gasses contained therein. As may occur quite often, the system access port may not be readily accessible due to the physical inaccessibility of the port or simple failure of the valve portion thereof rendering the port unreliable in terms of the ability to be resealed.
Consequently, a variety of valves have been developed to provide a ready means of tapping the pipeline of closed systems and to immediately provide valved access thereto. An exemplary valve is shown and described in U.S. Pat. No. 3,973,584, entitled "Piercing Valve for Tapping Pipelines", issued Aug. 10, 1976. The valve described provides upper and lower block portions that are adapted to receive corresponding portions of any desired short straight length of the pipeline. A screw tap bearing a piercing needle is provided to initially tap the pipeline. The hole created thereby is allowed to freely communicate with a port access inlet passage provided in the top block portion when the screw is backed off. A first seal is provided around the pierced hole at the pipeline/top block interface. A second seal is provided between the screw tap and the top block interface at the point that the screw tap is externally accessible. A third seal is provided by way of and within an external screw-on cap covering the port access inlet passageway when not otherwise being used. Thus, the valve may be essentially permanently attached to the pipeline, ensuring proper initial registration of the tap and pipeline and subsequent capping of the tapped hole to ensure the most minimal gas leakage from the system.
There are, however, a number of inherent practical problems with the known valves. They include the necessity to be adaptable to a variety of pipeline diameters, to effectively seal the tapped hole over long periods of time, to be resistant to tampering as well as inadvertent mistake, and minimize the possibility of system contamination throughout the process of tapping the port hole, recharging the system and capping off the port hole. Not least of all, the valve must be cost effective in its day-to-day usage.